Question: What is the greatest common factor of $30$ and $15$ ? Another way to say this is: $\operatorname{gcf}(30, 15) = {?}$
Explanation: The greatest common factor is the largest number that is a factor of both $30$ and $15$ The factors of $30$ are $1$ $2$ $3$ $5$ $6$ $10$ $15$ , and $30$ The factors of $15$ are $1$ $3$ $5$ , and $15$ Thus, the greatest common factor of $30$ and $15$ is $15$. $\operatorname{gcf}(30, 15) = 15$